This invention relates to a yarn cutting and gripping device for use on a circular knitting machine, in particular a double-cylinder one, the device being of the type comprising several adjacent strip-like elements which are movable back-and-forth along their lengths, adjacently a fixed blade and provided each with a hooked end lying on the plane of the strip-like elements, the hooked end having a cutting edge adapted to cooperate with the fixed blade to perform the cutting of the yarn, the strip-like elements being pressed against the fixed blade by an elastically urged body located on the opposite side to the fixed blade, said body acting as a gripping means of the yarn cut by the device.
A device to this general design is disclosed in U.S. Pat. No. 3,803,878 to Francesco Lonati. In this device, the strip-like elements are movable along a direction which is inclined to the cylinder(s) of the machine in a supporting structure attached to one side of the cylinder(s) at the yarn feed area. Each strip-like element is operable independently of the others through a respective lever controlled by the machine program.
When a yarn being processed is to be cut, for replacement with another yarn, for instance of a different color or count, the hooked end is caused to seize the yarn to be cut and moved down to contact the fixed blade, thus effecting the yarn cutting operation on one side and yarn gripping operation on the opposite side, where the yarn is retained between the strip-like element and the gripping body.
The gripping body may advantageously be a block of a resiliently yielding material, e.g. of a plastic material such as the one known in the trade as nylon, thereby the retention of the cut yarn is improved.
A device of this type has proved capable of providing a quick and accurate cutting operation, along with an effective gripping action.
However, it has been found that in some conditions, for some types of yarn, and especially in the case of a simultaneous retention of two yarns having different counts, the retaining action may be inadequate. This particularly when an excessive tension is applied to the yarn between the feeding reel and gripping unit.